My plan?

I've ben reading some older posts and saw that someone said doing tabata intervals with kettlebell swings is just as good as doing a 20 minute sprint interval workout. Is this true? I can definitely commit to 4 minutes of kettlebells easier than 20 minutes of sprints! I need to lose about 40lbs. and I would like to do it by the end of this year, tell me if this is a good plan:

Daily:
walk my dog for at least 4 miles a day at a speed of 4 mph. (don't worry she's a highly active breed )

Doing Tabata intervals this much is not a good idea and you can't compare a 4 min swing Tabata to 20 minutes of sprints. My advice would be to alternate what you have here with some actual sprinting.

I second the "actual sprinting" comment. I hadn't sprinted since college and the feeling of every 2 weeks or so (alternating weeks) feeling that you have actually improved your speed is much more satisfying and confidence boosting than being a little less tired after a Tabata for me.